Radio circuit



W. KAUFMAN RADIO CIRCUIT April 7, 1931.

Filed Dec.

.m m9. n rr Q. 7 $9 QL Q 9 3 M 1 m, s Q I W I m .I I 9 3 N Q aw w w H M Q M Q m t N m a w s T .9. a N\ .99 I Q mu M NQ N m m Patented Apr. 7, 1931.

PATENT OFFICE WOLFE KAUFMAN, OF PATTERSON, NEVT JERSEY, ASSIGNOR TO SAMUEL E. DARBY, (TIL,

OF SCARSDALE NEW YORK RADIO CIRCUIT Application filed December 3, 1928. Serial No. 323,341.

This invention relates in general to radio circuits and more particularly to the type known as cascaded radio frequency amplifying apparatus.

One of the objects of this invention is the provision of novel additions to tuned radio frequency amplifying circuits by means of which the generation of disturbing currents due to the feed back between the plates and grids of the audions is prevented. V

A further object of this invention involves neutralizing apparatus by, means of which multi-stagetuned radio frequency receiving apparatus is freed from the production of parasitic currents by reason of inter-stage coupling.

Another object of this invention is the provision of apparatus of this nature which is relatively simple in construction, efiicient in operation, andcheap to manufacture.

These and other objects, as will appear from the following disclosure, are secured by means of this invention.

This invention resides substantially in the combination, construction, arrangement, relative location of parts, and circuital connections, all as will be clearly apparent from the following disclosure.

Referring to the drawings, the single figure is a schematic diagram-showing the instrumentalities which comprise this invention and their association.

In the present day radio receiving equipment in the best form it is usual to precede the detector tube of the receiver by a number of stages of tuned radio frequency. As

is well known, such a tuned radio frequency amplifier is particularly subject to the generation of oscillating currents into different stages by reason of the feed back between the elements of the audions with the result that undesirable noises are produced as well as distortion. There are now known many v socalled neutralization schemes by reason of which the inter-electro capacity of the audions is compensated for so as to prevent undesired feed back of energy from output to input circuits. While these known systems have their advantages it is recognized that more simple apparatusis desired. The pur-' pose of this invention isto provide efiicient neutralizing means which is exceedingly simence is made to the drawings in which the antenna or energy collector is indicated at 1 connected through the inductance 2 to ground at- 3'. The inductance 2 comprising the primary of a radio frequency transformer is inductively coupled .to the secondary inductance 4, one terminal of which is connected through the wire or gridlO of audion 9. The otherwire 6 of this inductance is connectedto the'cathode 12 of the audion 9. A variable capacitance 7 is connected across the inductance 4 as well as the non-inductive high resistance 8. In one embodiment of this invention the resistance 8 is of the order of 0.25 megohm. The cathode 12 is connected by means of wires 13 through variable resistance 16 to the current source 14. Likewise, the cathodes .24, 30, and 42 are connected across the Wires 13 so that all the cathodes are in parallel. An additional variable resistance 15v is connected in one of the leads of cathode 42 so that its temperature may be varied independently of the temperature of the other cathodes. The plate 11 is connected through inductance 17, which has its other terminal connected by wire 50 to the current source 47. 'Another inductance 18 in conjunction with the inductance 17 provides a radio. frequency transformer for .coupling the output of the audion 9 to the input of audion21. Inductance 18 is connected across grid 22 and cathode 24 and is shunted by the variable capacitance 19 and non-inductive high resistance 20. The resistance of the element 20 is of the order. of 0.5 megohm.

The plate 23 is connected to the inductance megolnn. The plate 32 is connected through inductance 37 to the wire 50. Inductance 38, together With inductance 37, comprises a radio frequency transformer coupling the output of the audion 29 with the input of the audion 41. The inductance 38 is connected to the grid 33 through the grid leak system 40 and to the cathode. Inductance 38 is shunted by means of the variable capacitance 39. The plate 44 is connected through the loud speaking device 45 by wire 46 to a variable tap on the current source 47. The capacitance 49 connected between the cathode 42 and plate 44 provides a high frequency by-p ass and capacitance 48 is connected across the current source 47 to provide a high frequency by-pass. All the plates 11, 23, and 32 are connected to the positive side of the current source 4'? which has its negative side connected to the positive side of the current source 14 and cathode 42.

Particularly this invention involves a connection between the plate 11 and grid 22 including the variable non-inductive high resistance 34. The resistance of the element 34 is variable between the limits of approximately 0.1 to 0.5 megohm. Similarly, a noninductive high resistance 36 is connected between the plate 23 and grid 31. The resistance of the element 36 is approximately 0.1 megohm. Grid 10 and grid 22 are connected through a non-inductive high resistance 33 which has a value of the order of 0.5 megohm. Grid 22 and grid 31 are connected through a non-inductive high resistance 35 of a value of the order of 0.25 megohm. As clearly indicated in the drawings the audions 9, 21 and 29 with their associated circuits comprise a three-stage tuned radio frequency amplifier, the output of which is impressed upon the input or grid circuit of the detector audion 41. Although no showing has been made it is apparent that the output of the detector 41 can be impressed upon the input of a multi-stage audio frequency amplifier before passing to the loud speaker if desired. It is, of course, apparent that the principles of this invention are not limited to the number of stages involved but rather to the manner of interconnecting the stages through high resistance to prevent the feed back from output to input circuits of radio energy which would cause distortion of the final output current and other defects. Likewise the values given as illustrative of the resistances used in this invention are only given for purposes of description and not limitation.

I am, of course, well aware that changes in the details of construction and relative arrangement of parts will occur to those skilled in this art and I do not, therefore, desire to be strictly limited by my disclosure but rather to the scope of the appended claims.

What I seek to secure by United States Letters Patent is:

1. In an arrangement of the type described, the combination comprising a plurality of audlos each having a grid, plate and cathode, input and output circuits for said audions coupled together to provide a multi-stage radio frequency amplifier, and conductive high resistance connections between the grid electrodes of said audions.

2. In an arrangement of the type described, the combination comprising a plurality of audions each having a grid, plate and cathode, input and output circuits for said audions coupled together to provide a multi-stage radio frequency amplifier, high resistance connections between the grid electrodes of said audions, and high resistance connections between the grids and plates of the electrically adjacent audions.

3. In an arrangement of the type described, the combination comprising a plurality of audions each having a grid, plate and cathode, input and output circuits for said audions coupled together to provide a multi-stage radio frequency amplifier high resistance connections between the grid electrodes of said audions, high resistance con nections between the grids and plates of the electrically adjacent audions, and a high resistance path connected between the grid and cathode of each audion.

4. In a tuned radio frequency amplifier, the combination comprising a plurality of audions having grid, plate and cathode electrodes, input and output circuits for said audions coupled together to provide a multi-stage amplifier, means for tuning the input circuits of said audions, and a conductive high resistance connection between all of the grid electrodes of said audions.

5. In a tuned radio frequency amplifier, the combination comprising a plurality of andions having grid, plate and cathode electrodes, input and output circuits for said audions coupled together to provide a multi-stage amplifier, means for tuning the input circuits of said audions, a high resistance connection between all of the grid electrodes of said audions, and a connection between the plate and grid of the last two audions of said amplifier including a high resistance.

6. In a tuned radio frequency amplifier, the combination comprising a plurality of audions having grid, plate and cathode electrodes, input and output circuits for said audions coupled together to provide a multi-stage amplifier, means for tuning the input circuits of said audions, a high resistance connection between all of the grid electrodes of said audions, a connection between the plate and grid of the last two audions of said amplifier including a high resistance, and a variable resistance between the plate and grid electrode of the first two audions of said amplifier.

7. In a tuned radio frequency amplifier, the

combination comprising a plurality of audions having grid, plate and cathode electrodes, input and output circuits for said audions coupled together to provide a multistage amplifier, means for tuning the input circuits of said audions, a high resistance connection between all of the grid electrodes of said audions, a connection between the plate and grid of the last two audions of said amplifier including a high resistance, a variable resistance between the plate and grid electrode of the first two audions of said amplifier, and a high resistance connection between the grid and cathode elements of each audion.

In testimony whereofI have hereunto set my hand on this 26th day of November, A. D.

WOLFF KAUFMAN. 

